The 686+ is slightly smaller and has a slightly smaller grip frame. L Frames like the 686+ use the same grips that fit the K Frame. These grips will not fit the N Frame. The L Frame will have a shorter reach to the trigger, compared to the N Frame 627, if similar grips are used.
Because of these smaller dimensions many find the 686+ easier to shoot and will give up one less round in capacity, seeing that as a fair trade-off.
Both chamber the .357 Magnum and .38 Special. Both can be used with moonclips, if the cylinder is appropriately machined for their use.